Wafer thinning apparatus and thinning method

Abstract

The application provides a wafer thinning device and a thinning method, and belongs to the technical field of integrated circuit manufacturing. The thinning method comprises the following steps: obtaining light intensity values corresponding to light signals in the process of grinding a wafer by using a grinding wheel; determining baseline drift and peak decay based on the light intensity values; and determining the service life state of the grinding wheel based on the comparison results of the baseline drift and the peak decay with corresponding threshold values. The light signals are emitted by the thermoluminescent nanoparticles in the grinding wheel of the wafer thinning device under the excitation of grinding heat. The application can improve the wafer grinding precision, reduce the defective rate and improve the grinding efficiency.

Description

Technical Field

[0001] This application belongs to the field of integrated circuit manufacturing technology, and more specifically, relates to a wafer thinning device and a thinning method. Background Technology

[0002] Three-dimensional integrated circuits (3D ICs) are an important technological path for the semiconductor industry to continue Moore's Law and improve chip performance and integration. The core idea is to stack multiple chips or functional layers vertically and achieve interlayer electrical connections through interconnection technologies such as through-silicon vias (TSVs), thereby achieving higher functional density within a limited space.

[0003] Wafer thinning is a key supporting process in 3D IC manufacturing, its main purpose being to reduce the wafer's thickness from its original level to an ultra-thin state suitable for vertical integration. Ultra-thin wafers are the physical basis for 3D stacking and are crucial for optimizing electrical performance and thermal management. As the number of 3D IC stacking layers increases, the requirements for the thinning thickness of individual wafers become increasingly stringent. Simultaneously, 3D IC technology places extremely high demands on the surface quality of the thinned wafer, including excellent Total Thickness Variation (TTV) and extremely low Roughness Average (Ra), to ensure the accuracy, consistency, and stability of subsequent bonding processes.

[0004] To achieve the aforementioned thinning targets, wafer thinning equipment typically utilizes the physical grinding action of grinding wheels to process ultra-thin wafers. Such equipment must have its grinding structure and grinding process precisely designed and controlled to meet the requirements for ultra-thin wafer processing (such as thickness ≤10μm, TTV ≤1.5um, and Ra ≤1μm) while also considering manufacturing costs and production efficiency.

[0005] In wafer thinning processes, grinding wheels are the core consumables that directly perform grinding operations, and the stability and consistency of their performance are crucial to ensuring the quality of ultra-thin wafer processing. However, existing methods for monitoring grinding wheel life have significant limitations, mainly manifested in insufficient monitoring accuracy and lagging replacement strategies.

[0006] Existing monitoring methods mostly rely on simple macroscopic statistical parameters such as grinding time or the number of wafers processed to estimate the lifespan, which cannot reflect the actual wear state and microscopic failure mechanisms of the grinding wheel abrasive grains in real time and accurately. This inaccuracy in monitoring makes it impossible to accurately determine the critical decay point of the grinding wheel performance, resulting in significant uncertainties in the process.

[0007] Even more serious is the fact that, due to inaccurate monitoring, the current common strategy is to adopt a fixed-cycle replacement or a reactive shutdown in case of failure, which inevitably leads to delayed replacement. The grinding capability of a worn grinding wheel decreases significantly in its later stages, making it difficult to meet the stringent TTV and Ra requirements of ultra-thin wafers. Furthermore, it is more prone to introducing surface / subsurface damage, stress concentration, and other defects during the thinning process, directly jeopardizing the bonding quality of 3D IC stacking and the reliability of the final product. Therefore, monitoring the grinding wheel's lifespan during wafer grinding is of paramount importance. Summary of the Invention

[0008] Based on the above problems, this application provides a wafer thinning apparatus and a thinning method, which aims to at least solve or alleviate one of the technical problems existing in the prior art.

[0009] A first aspect of this application provides a wafer thinning apparatus, including: a grinding device, an adsorption platform, a collector, and a controller.

[0010] The adsorption platform is used to support the wafer and drive its rotation;

[0011] The grinding device is raised and lowered above the adsorption platform, and its lower part has a grinding wheel for grinding wafers; the grinding wheel includes a grinding block, which contains thermoluminescent nanoparticles that emit light signals of different intensities under different grinding thermal excitations;

[0012] The collector is used to collect optical signals;

[0013] The controller is electrically connected to the collector and is used to determine the baseline drift and peak attenuation based on the optical signal. The controller compares the baseline drift and peak attenuation with the corresponding thresholds to determine the grinding wheel life status based on the comparison results.

[0014] In one embodiment, the grinding block comprises diamond abrasive grains with nanoparticles loaded on its surface.

[0015] In one embodiment, the nanoparticles are composed of lanthanide metal oxides.

[0016] In one embodiment, the nanoparticles include one or more of europium oxide, cerium oxide, gadolinium oxide, and samarium oxide.

[0017] In one embodiment, the grinding apparatus includes:

[0018] The feed assembly is positioned above the adsorption platform and moves up and down relative to it. The feed assembly is electrically connected to the controller, which is configured to control the feed speed of the feed assembly based on the grinding wheel's lifespan.

[0019] The rotating shaft is connected to and driven by the feed assembly for lifting and lowering, and the grinding wheel is connected to the lower end of the rotating shaft.

[0020] In one embodiment, the peak attenuation includes: peak difference attenuation and peak delay; the controller includes:

[0021] The comparator, electrically connected to the data logger, compares the baseline drift and peak attenuation with corresponding thresholds to determine the grinding wheel life status based on the comparison results, including:

[0022] In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition.

[0023] In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear.

[0024] In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

[0025] In one embodiment, the controller further includes:

[0026] A first actuator, electrically connected to a comparator and a feed assembly, is used to adjust the feed rate of the feed assembly based on the grinding wheel's life condition; and / or

[0027] The second actuator, electrically connected to the comparator and the indicator, is used to issue corresponding prompts based on the grinding wheel's life status.

[0028] A second aspect of this application provides a thinning method, comprising the following steps:

[0029] The light intensity value corresponding to the light signal during the grinding process of a wafer is obtained; the light signal is emitted by thermoluminescent nanoparticles in the grinding wheel under the thermal excitation of grinding.

[0030] Baseline drift and peak attenuation are determined based on light intensity values;

[0031] The baseline drift and peak attenuation are compared with their respective thresholds to determine the grinding wheel life status based on the comparison results.

[0032] In one embodiment, determining the baseline drift based on the light intensity value includes:

[0033] Determine the current light intensity baseline based on the light intensity value;

[0034] The baseline drift is determined based on the comparison between the current light intensity baseline and the reference light intensity baseline.

[0035] In one embodiment, the peak attenuation amount includes: peak difference attenuation amount; determining the peak attenuation amount based on the light intensity value includes:

[0036] The current peak value difference is determined based on the difference between the peak light intensity at the moment of wafer feed during grinding and the current light intensity baseline.

[0037] The peak difference attenuation is determined based on the comparison between the current peak difference and the baseline peak difference.

[0038] In one embodiment, the peak attenuation amount includes: a peak delay amount; determining the peak attenuation amount based on the light intensity value includes:

[0039] The time elapsed since the start of feed when the peak light intensity of the current wafer appears during grinding is obtained, and this time is taken as the current peak light intensity occurrence time of the current wafer during grinding.

[0040] The peak delay is determined based on the comparison between the current peak occurrence time and the baseline peak occurrence time.

[0041] In one embodiment, the peak attenuation includes: peak difference attenuation and peak delay; comparing the baseline drift and peak attenuation with corresponding thresholds to determine the grinding wheel life state based on the comparison results includes:

[0042] In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition.

[0043] In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear.

[0044] In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

[0045] In one embodiment, the method further includes:

[0046] Adjust wafer grinding parameters based on grinding wheel life status; and / or

[0047] The system will issue corresponding prompts based on the grinding wheel's lifespan.

[0048] The beneficial effects of the wafer thinning equipment and thinning method provided in this application are as follows:

[0049] The wafer thinning device of this application adds nanoparticles to the composition of the grinding wheel block. The nanoparticles have thermoluminescence properties and emit light signals of different intensities due to different grinding heat during the grinding process of the wafer. The baseline drift and peak attenuation can be determined based on the light intensity value. The baseline drift and peak attenuation are compared with corresponding thresholds to determine the grinding wheel life status based on the comparison results.

[0050] This application embodiment enables the determination of grinding wheel life status based on changes in light intensity characteristics, achieving real-time monitoring of grinding wheel life status. This allows for further adjustment of grinding parameters based on grinding wheel life status, and timely replacement of the grinding wheel in cases of severe wear. This avoids the impact of grinding wheel performance changes on grinding accuracy and damage to the wafer surface caused by severe grinding wheel wear, effectively improving wafer grinding accuracy and efficiency, reducing unexpected downtime, and increasing yield.

[0051] This application embodiment adds nanoparticles to the grinding wheel block, utilizing the interfacial stress-induced effect to achieve lattice dislocation pinning strengthening, thereby enhancing the toughness and bonding strength of the grinding block. On the one hand, this can improve the service life of the grinding wheel and reduce the frequency of grinding wheel replacement in wafer thinning equipment. On the other hand, it can also reduce the breakage and shedding of abrasive grains in the grinding wheel block, improve grinding stability, and thus achieve the effect of improving wafer grinding accuracy and yield. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the structure of a wafer thinning apparatus according to one embodiment of this application;

[0054] Figure 2 for Figure 1 Side view of the grinding device and adsorption platform of the wafer thinning equipment;

[0055] Figure 3 for Figure 2 Bottom view of the intermediate grinding wheel;

[0056] Figure 4 This is a structural block diagram of a wafer thinning apparatus provided in one embodiment of this application;

[0057] Figure 5 A schematic diagram illustrating the light intensity characteristics of a grinding wheel under different wear states, provided in one embodiment of this application;

[0058] Figure 6 This is a flowchart of a thinning method provided in one embodiment of this application;

[0059] Figure 7 This is an overall flowchart of a thinning method provided in one embodiment of this application;

[0060] Figure 8 This is a structural block diagram of a thinning device provided in one embodiment of this application;

[0061] Figure 9 This is a schematic block diagram of an electronic device provided in an embodiment of this application.

[0062] Figure label:

[0063] 1. Equipment base; 2. Grinding device; 21. Rotary shaft; 22. Grinding wheel; 221. Substrate; 222. Grinding block; 3. Adsorption platform; 31. Chuck spindle; 32. Worktable; 33. Adsorption plate; 4. Rotary disk; 80. Thinning device; 81. Acquisition unit; 82. Light intensity change analysis unit; 83. Grinding wheel life status determination unit; 600. Electronic equipment; 601. Processor; 602. Input device; 603. Output device; 604. Memory; 605. Communication bus. Detailed Implementation

[0064] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0065] To keep the drawings concise, each drawing only schematically shows the parts relevant to the disclosure; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0066] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0067] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0068] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0069] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0070] It should be understood that, unless the context clearly states otherwise, the terms "comprising," "including," or "having" as used herein refer to the presence of an element, but do not exclude the presence or addition of one or more other elements. Furthermore, "comprising" and / or "including" as used herein specify the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof. Some embodiments of this application are described in detail below with reference to the accompanying drawings. Where there is no conflict between the embodiments, the following embodiments and features can be combined with each other. The steps in the following method embodiments are for illustrative purposes only and are not intended to limit this application.

[0071] Reference Figure 1 and Figure 2 , Figure 1 The image shows a wafer thinning device. Figure 2 for Figure 1 The side view of the grinding device 2 and the adsorption platform 3 of the wafer thinning equipment. The wafer thinning equipment includes a device base 1, on which a rotating disk 4 is provided. Above the rotating disk 4, multiple adsorption platforms 3 are arranged at intervals along the circumference. The rotating disk 4 can rotate around its own central axis to change the position of the adsorption platform 3, so that the wafer supported by the adsorption platform 3 can switch between the rough grinding station, the fine grinding station and the loading and unloading station.

[0072] Furthermore, a column is provided at the end of the equipment base 1, and a grinding device 2 is provided on the side of the column. There are two grinding devices 2, corresponding to a rough grinding section and a fine grinding section. The two have similar structures and are both equipped with a feed assembly that drives the grinding wheel 22 to move up and down and a mechanism that drives the grinding wheel to rotate along the rotating shaft 21. The feed assembly is set above the adsorption platform and moves up and down relative to it. The feed assembly includes a lifting motor (not shown), which is slidably connected to the housing of the rotating shaft through a lead screw. The housing is slidably connected to the side of the column so that the rotation of the lifting motor realizes the vertical movement of the rotating shaft 21, thereby changing the position of the grinding wheel 22 relative to the adsorption platform 3.

[0073] The adsorption platform 3 is used to support the wafer and drive the wafer to rotate. The grinding device 2 is raised and lowered above the adsorption platform 3. The lower part of the grinding device 2 has a grinding wheel 22 that can rotate circumferentially to grind the wafer.

[0074] The grinding device 2 includes a feed assembly, a rotary shaft 21, and a grinding wheel 22. The grinding block 222 in the grinding wheel 22... Figure 3 (Shown) This is used for grinding wafers. The grinding wheel 22 can be a cup-shaped grinding wheel, mounted at the lower end of the rotating shaft 21. The rotating shaft 21 is used to rotate the grinding wheel 22 about its axis of rotation. The rotating shaft 21 is drive-connected to a feed assembly, which drives the rotating shaft 21 and the grinding wheel 22 to move up and down synchronously. When the wafer needs grinding, the grinding wheel 22 moves under the drive of the feed assembly until its bottom surface contacts the surface of the wafer. At this time, both the grinding wheel 22 and the wafer are rotating in the same direction but at different speeds, and the surface of the wafer is ground using the grinding wheel 22. The feed assembly has a known construction and includes, for example, multiple linear guides that guide the movement direction of the rotating shaft 21 and a ball screw-slider mechanism that moves the rotating shaft 21 up and down.

[0075] Reference Figure 3 , it is Figure 2 A bottom view of the grinding wheel 22 shows that the grinding wheel 22 includes a substrate 221 and a plurality of grinding blocks 222 disposed on the surface of the substrate 221 for grinding the wafer. The grinding blocks 222 can be rounded rectangles or fan shapes. At least a portion of the grinding blocks 222 is embedded in an annular groove and spaced apart from each other on the substrate 221. The substrate 221 can be fastened to the lower end of the rotating shaft 21 by bolts.

[0076] In one embodiment, the raw materials of the grinding block 222 include: diamond abrasive grains, nanoparticles, resin binder, and pore-forming agent. The nanoparticles are loaded on the surface of the diamond abrasive grains, thus the surface of the grinding block 222 contains nanoparticles, and these nanoparticles exhibit thermoluminescence properties. During the grinding process of the wafer by the grinding wheel 22, different grinding heat can excite light signals of different intensities.

[0077] In one embodiment, the nanoparticles are composed of lanthanide metal oxides, which exhibit thermoluminescence. This application innovatively introduces lanthanide metal oxide nanoparticles as a functional interface reinforcement phase, loaded onto the surface of diamond abrasive grains. Lanthanide metal oxides not only possess high hardness, high melting point, and excellent thermal stability, but also exhibit unique thermoluminescence properties. This property refers to the phenomenon of photons emitted by the material due to thermal excitation during heating or grinding, which can serve as a sensitive signal source for in-situ monitoring of interfacial stress and temperature changes, indirectly reflecting the thermo-mechanical coupling state of the grinding zone.

[0078] From an interfacial chemistry perspective, the surface of lanthanide metal oxide nanoparticles is rich in Lewis acid sites (such as uncoordinated sites). Ions can undergo strong chemical adsorption or coordination with oxygen-containing functional groups (such as carboxyl and hydroxyl groups) introduced into the diamond surface after pretreatment (such as acidification or hydroxylation), forming a strong Ln–O–C covalent interface bridge. This interface layer not only significantly enhances the chemical bonding force between diamond and the binder (such as ceramic, metal, or resin-based materials), reducing the tendency of abrasive grains to detach under high-speed and high-load conditions, but also effectively transmits and disperses grinding stress, delaying the initiation and propagation of microcracks, thereby improving the overall mechanical properties of the grinding wheel, such as bending strength, impact toughness, and wear resistance.

[0079] In this embodiment, lanthanide metal oxides are used as nanoparticles loaded onto the diamond surface, which improves the overall mechanical properties and grinding stability of the grinding wheel. Compared with other metal oxides, the unfilled 4f orbitals in lanthanide metals can form strong coordination bonds with hydroxyl oxygen atoms at defect sites on the diamond surface. This interaction can build a stable interface between the diamond and the binder, effectively preventing diamond detachment during grinding and inhibiting crack propagation, thereby significantly extending the service life of the grinding wheel 22. This embodiment adds specific nanoparticles to the grinding wheel block to achieve nanoscale functional modification and strengthening of the diamond abrasive surface. Specifically, the selected nanoparticles (such as lanthanide metal oxides) are firmly loaded onto the diamond surface through chemical adsorption or physical anchoring. During grinding, the difference in thermal expansion coefficients between them and the diamond, as well as the interfacial lattice mismatch, induces a controllable micro-interfacial stress field. This stress field can further induce lattice distortion, forming stable dislocation pinning centers, effectively hindering the initiation and propagation of microcracks inside the diamond, thereby achieving a dislocation strengthening mechanism.

[0080] Meanwhile, lanthanide metal oxide nanoparticles possess high thermal stability and mechanical strength, and under high-temperature grinding conditions, they can undergo localized chemical bonding with the diamond surface, forming strong interfacial coupling. Under periodic grinding stress, the stress field gradient formed around these nanoparticles can significantly constrain the slip and multiplication of dislocations in the diamond lattice, causing dislocation lines to bend and entangle around the particles, consuming crack propagation energy, thereby greatly improving the macroscopic toughness and fracture resistance of diamond abrasive grains.

[0081] Furthermore, this strengthening mechanism also helps enhance the physicochemical bonding strength between diamond and the binder (such as metal, ceramic, or resin-based materials). Nanoparticles, acting as an interfacial transition layer, can alleviate stress concentration caused by differences in material properties, improve load transfer efficiency, and reduce the tendency for abrasive grains to detach. Ultimately, the overall mechanical properties of the grinding wheel 22, such as impact resistance, wear resistance, and fatigue life, are significantly optimized, vibration and noise during the grinding process are reduced, and process stability and the surface quality of the machined parts are simultaneously improved.

[0082] In summary, this embodiment achieves a systematic improvement in the performance of diamond abrasive grains from microscopic strengthening to macroscopic performance through the stress-induced dislocation pinning effect induced by nanoparticle interface modification, providing a new approach for the design of high-precision and high-efficiency grinding tools.

[0083] In one embodiment, the nanoparticles comprise: europium oxide cerium oxide Gadolinium oxide samarium oxide One or more of the following, preferably, the nanoparticles are europium oxide. Europium oxide exhibits unique interface enhancement advantages in this application, mainly due to its special electronic structure and variable valence properties: A reversible and sensitive redox synergistic mechanism exists. During high-temperature grinding or interfacial reactions, Eu ions can dynamically switch between their +2 and +3 valence states according to the local chemical environment. On the one hand, this enhances the charge interaction with carbon atoms on the diamond surface, forming a stronger interfacial bond. On the other hand, this valence state change can induce lattice distortion and stress field modulation, further promoting dislocation pinning and interfacial strengthening effects, thereby significantly improving the interfacial bonding strength and load transfer capability between the nanoparticle-supported layer and the diamond matrix.

[0084] Furthermore, europium oxide exhibits excellent thermal stability and radiative energy dissipation characteristics, maintaining the integrity of the interfacial structure under the high temperature and high stress conditions caused by high-speed grinding, and avoiding a decrease in bonding strength due to thermal softening or degradation of the interfacial reaction layer. Compared with other lanthanide oxides, europium oxide... The synergistic effect of the dual-valent state is more significant, making it more advantageous in strengthening the diamond-bond interface under the same conditions. This, in turn, more effectively inhibits abrasive shedding, delays the propagation of microcracks, and ultimately improves the overall wear resistance of the grinding wheel and the stability of the grinding process.

[0085] The adsorption platform 3 has a chuck spindle 31, a worktable 32, and an adsorption disk 33. The chuck spindle 31 moves along the axis of rotation. The adsorption disk 33, made of a porous ceramic material, is embedded in the upper surface of the worktable 32. The adsorption platform 3 has a conduit that penetrates its interior and extends to its surface. The conduit is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint. When the vacuum source is activated, the wafer placed on the adsorption platform 3 is adsorbed by the adsorption disk 33. Conversely, when the compressed air source or water supply source is activated, the adsorption between the wafer and the adsorption disk 33 is released. The adsorption platform 3 may be equipped with a tilting device that tilts relative to the grinding wheel 22, or the grinding device 2 may be equipped with a tilting structure that tilts the rotation axis 21. This allows adjustment of the contact between the grinding block 222 and the wafer to grind the wafer into the desired shape.

[0086] refer to Figure 2 and Figure 4 , Figure 4 This is a structural block diagram of a wafer thinning apparatus. In one embodiment, a collector can collect the light signal emitted by the nanoparticles. In one embodiment, the collector faces the grinding block 222 of the grinding wheel 22. For example, the collector can be positioned to the side of the adsorption platform 3 and below the grinding wheel 22. Figure 2 As shown, the light signal emitted by nanoparticles is collected in real time from bottom to top. The collector can be a photoelectric sensor, which is composed of a photodiode array.

[0087] In one embodiment, the wafer thinning apparatus further includes a controller electrically connected to the collector for determining the baseline drift and peak attenuation of the optical signal emitted by the nanoparticles. Baseline drift and peak attenuation are two key factors in measuring the grinding wheel's lifespan. Based on comparisons of the baseline drift and peak attenuation with corresponding thresholds, the grinding wheel's lifespan can be determined, thereby enabling monitoring of the grinding wheel's lifespan.

[0088] Baseline drift refers to the deviation between the current light intensity baseline measured in real time and the reference light intensity baseline. The current light intensity baseline refers to the average light intensity value of the grinding wheel during the stable grinding phase when grinding the current wafer. The reference light intensity baseline refers to the pre-calibrated average light intensity value of the grinding wheel during the stable grinding phase. For a given grinding wheel, the average light intensity value during the stable grinding phase is a fixed value, hence it is called the reference light intensity baseline.

[0089] Peak attenuation includes: peak difference attenuation and peak delay; wherein, peak difference attenuation refers to the deviation between the current peak difference value measured in real time and the reference peak difference value; the current peak difference value refers to the difference between the peak light intensity value at the moment of current wafer feed and the current light intensity baseline; the reference peak difference value refers to the difference between the peak light intensity value at the moment of pre-calibrated grinding wheel feed and the reference light intensity baseline.

[0090] Peak delay refers to the deviation between the current peak occurrence time and the reference peak occurrence time of the current wafer being ground. The current peak occurrence time is the time from the start of feed after the peak light intensity appears during grinding. The reference peak occurrence time is the specified time from the start of feed after the peak light intensity appears.

[0091] The initial stage, known as the feed moment, refers to the initial stage when the abrasive grains of the grinding wheel just contact the wafer, causing a sudden increase in grinding heat. The stable grinding stage refers to the steady grinding stage outside of the feed moment, where there is no sudden increase in grinding heat.

[0092] In one embodiment, the controller can control the various components constituting the grinding apparatus 2. The controller includes, for example, a CPU and a memory. Furthermore, the controller's functions can be implemented through software control or through hardware operation. For example, the controller can adjust grinding parameters based on the monitored grinding wheel life status, such as controlling the feed assembly to adjust the feed speed. Simultaneously, the controller also has an alarm function, capable of issuing corresponding alarms based on the real-time monitored grinding wheel life status.

[0093] In one embodiment, to determine the light intensity value corresponding to the light signal collected by the collector, the controller further includes: a comparator electrically connected to the collector, used to compare the baseline drift and peak attenuation with corresponding thresholds, and determine the grinding wheel life state based on the comparison results. In one embodiment, the peak attenuation includes: peak difference attenuation and peak delay. The comparator can be used to: determine the baseline drift, peak difference attenuation, and peak delay based on the light intensity value; compare the baseline drift with a first drift threshold and a second drift threshold, respectively; compare the peak difference attenuation with a first attenuation threshold and a second attenuation threshold, respectively; and compare the peak delay with a delay threshold, to determine the grinding wheel life state based on the comparison results, including:

[0094] In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition.

[0095] In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear.

[0096] In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

[0097] refer to Figure 5 , Figure 5 This diagram illustrates the light intensity characteristics of a grinding wheel under different usage conditions, according to one embodiment of this application. As can be seen from the diagram, when the grinding wheel is in an unworn state, such as… Figure 5 The solid line represents the light intensity characteristics, corresponding to the baseline light intensity Ibase0, the difference between the baseline peak intensity and D0, and the time of occurrence of the baseline peak intensity Tp0. When the grinding wheel is in a slightly worn state, it corresponds to... Figure 5 The dashed line represents the light intensity characteristics, and the current light intensity baseline is Ibase. t1 The current peak difference is D. t1 The current peak time is Tp1. When the grinding wheel is at the end of its lifespan, the corresponding... Figure 5 The dotted line represents the light intensity characteristics, and the current light intensity baseline is Ibase. t2 The current peak difference is D. t2 The current peak occurs at time Tp2. As can be seen from the changes in light intensity characteristics under the three states in the figure, as the wear of the grinding wheel increases, the drift between the current light intensity baseline and the reference light intensity baseline becomes more severe, the peak difference attenuation also increases, and the peak delay also increases. This is equivalent to Ibase. t2 The drift relative to Ibase0 is greater than Ibase0. t1Drift relative to Ibase0; D t2 The decay relative to D0 is greater than that of D. t1 The decay relative to D0; and the delay of Tp2 relative to Tp0 is greater than the delay of Tp1 relative to Tp0.

[0098] This embodiment simultaneously monitors changes in light intensity characteristics such as baseline drift and peak attenuation, and compares them with corresponding thresholds. Compared to a single-parameter judgment method, it can more comprehensively capture the changing patterns of light signals during grinding wheel wear, reduce misjudgments caused by fluctuations in a single parameter, and significantly improve the accuracy of grinding wheel life status monitoring.

[0099] Furthermore, this embodiment compares the baseline drift and peak attenuation with corresponding thresholds, and divides the state of the grinding wheel into three stages: normal state, light wear state, and severe wear state based on the comparison results, instead of simply judging whether the grinding wheel is "normal" or "failed" as in conventional methods. This is beneficial for adjusting the grinding parameters when the grinding wheel is in a light wear state, thus maintaining stable grinding efficiency.

[0100] The aforementioned preset thresholds can be determined by human experience, statistical analysis of historical data, or by training a threshold prediction model based on historical data. The thresholds can then be obtained using the prediction model to improve adaptability to specific grinding wheel or wafer types.

[0101] In one embodiment, the controller further includes:

[0102] A first actuator, electrically connected to a comparator and a feed assembly, is used to adjust the feed rate of the feed assembly based on the grinding wheel's life condition; and / or,

[0103] The second actuator, electrically connected to the comparator and the indicator, is used to issue corresponding prompts based on the grinding wheel's life status.

[0104] Through the above-mentioned dual actuator linkage control, this embodiment achieves a fast and accurate response to the grinding wheel life status. When the grinding wheel is in different wear states, the appropriate grinding parameters can be adjusted to overcome the impact of grinding wheel abrasive wear on wafer grinding quality and grinding efficiency. In addition, the grinding wheel can be replaced in time when it is severely worn to avoid surface damage to the wafer caused by abrasive shedding.

[0105] The wafer thinning equipment of this application adds nanoparticles to the composition of the grinding wheel, thereby loading the surface of the diamond abrasive grains with nanoparticles. These nanoparticles have thermoluminescence properties, and during the grinding process of the wafer, different grinding heat excites light signals of different intensities. Based on the light intensity value, the baseline drift and peak attenuation can be determined. Based on the comparison results of the baseline drift and peak attenuation with corresponding thresholds, the grinding wheel life status can be determined. This application realizes the judgment of the grinding wheel life status based on the change of light intensity characteristics, and realizes the real-time monitoring of the grinding wheel life status. This allows for further adjustment of grinding parameters based on the grinding wheel life status, and timely replacement of the grinding wheel in the case of severe wear. This avoids the impact of grinding accuracy on the grinding wheel performance due to changes in grinding wheel performance, and the damage to the wafer surface caused by severe grinding wheel wear. It can effectively improve the grinding accuracy and efficiency of the wafer, reduce the number of unexpected downtimes, and improve the yield.

[0106] Meanwhile, this embodiment of the application adds nanoparticles to the grinding wheel block, thereby loading the surface of the diamond abrasive grains with nanoparticles. Utilizing the interfacial stress-induced effect, lattice dislocation pinning strengthening is achieved, enhancing the toughness and bonding strength of the diamond abrasive grains. On the one hand, this can improve the service life of the grinding wheel and reduce the frequency of grinding wheel replacement in wafer thinning equipment. On the other hand, it can also reduce abrasive grain breakage and shedding, improving grinding stability, thus achieving the effect of improving wafer grinding accuracy and yield.

[0107] The principle of this application for monitoring the life of grinding wheels is as follows: Utilizing the thermoluminescence properties of nanoparticles in the grinding wheel, the nanoparticles emit light under the excitation of grinding heat during the grinding of wafers. Furthermore, the grinding heat changes under the same feed rate at different wear levels of the grinding wheel. The change in grinding heat causes a change in the luminescence properties of the nanoparticles. By analyzing the correlation between the change in luminescence properties and the wear state of the grinding wheel, the life state of the grinding wheel can be monitored. Monitoring the life state of the grinding wheel includes determining the wear state of the grinding wheel.

[0108] The main manifestation of different wear conditions of grinding wheels is the change in abrasive grain state. The change in abrasive grain state will change the grinding pressure distribution and grinding heat generation efficiency, which will in turn be reflected in the change of luminescence characteristics. The change in luminescence characteristics can be reflected by baseline drift and peak attenuation. The specific principle is as follows:

[0109] The diamond abrasive grains of a new grinding wheel are sharp, resulting in a small contact area with the wafer and uniform grinding pressure distribution. During the stable grinding phase, the grinding heat generated per unit time is stable, thus maintaining a stable baseline for the luminescence intensity of the nanoparticles. As the abrasive grains wear down, the grinding efficiency of the wheel decreases. At the same feed rate, the effective cutting contact area between the abrasive grains and the wafer increases, reducing the efficiency of grinding heat generation. Consequently, the baseline of the average luminescence intensity during the stable grinding phase gradually decreases with increasing wear. Therefore, the degree of baseline drift can be used to determine the wheel's lifespan.

[0110] In addition, the grinding heat increases sharply when the new grinding wheel is fed, and the luminescence intensity of the nanoparticles will show a significant peak. As the grinding wheel abrasive grains wear down, the cutting force at the moment of feeding is dispersed, the grinding heat generation efficiency slows down, the difference between the peak and the baseline gradually decreases, and the time point of the peak appearance is gradually delayed, resulting in the phenomenon of peak difference attenuation and peak response lag. Therefore, the service life of the grinding wheel can be judged by the peak attenuation.

[0111] The above analysis shows that the thinning method of this application includes the following stages: determining the correlation between changes in luminescence characteristics and the wear state of the grinding wheel, benchmark calibration, real-time monitoring and analysis, and threshold comparison life assessment. The stage of determining the correlation between changes in luminescence characteristics and the wear state of the grinding wheel involves analyzing and obtaining the above principles, thereby establishing a correlation model between changes in luminescence intensity characteristics and the wear state of the grinding wheel. After determining this correlation model, subsequent grinding wheel life monitoring operations can be performed based on it.

[0112] The benchmark calibration stage includes calibrating the following parameters: benchmark light intensity baseline, benchmark peak difference, and benchmark peak occurrence time. One embodiment of this application provides a benchmark calibration method comprising: measuring n wafers before grinding with a grinding wheel, and using the average value of each benchmark measured on the n wafers before grinding as the calibration value. Where 3 ≤ n ≤ 10, for example, n can be 5, 6, 7, etc. Specific benchmark calibration content and methods are shown in Table 1.

[0113] Table 1. Reference Calibration Content and Methods

[0114]

[0115] It is understandable that the above calibration operation can be performed once for each grinding wheel, or once for grinding wheels of the same batch and model.

[0116] Understandably, selecting n wafers for benchmark calibration before grinding with the grinding wheel is to eliminate signal fluctuations during the "break-in period" of the new grinding wheel, so as to ensure that the calibrated benchmark can accurately reflect the stable working state.

[0117] In one embodiment, the calculation method for the reference peak difference can be: the percentage of the difference between the pre-calibrated peak light intensity at the moment of grinding wheel feed and the reference light intensity baseline to the reference light intensity baseline, the value of which is generally between 20% and 25%; the occurrence time of the reference peak is generally between 0.5ms and 1ms.

[0118] Based on the above benchmark calibration operations and the aforementioned principles, the real-time monitoring and analysis phase and the threshold comparison lifetime assessment phase can be executed. Each time the grinding wheel grinds a wafer, the following operation can be performed once.

[0119] Reference Figure 6 The following is a flowchart of a thinning method provided in an embodiment of this application. The method includes the following steps:

[0120] S61. Obtain the light intensity value corresponding to the light signal during the grinding process of the wafer.

[0121] The grinding wheel of the wafer thinning apparatus in this application embodiment contains thermoluminescent nanoparticles. During the wafer grinding process, the grinding heat excites these nanoparticles to emit light, and the intensity of the light signal emitted by different grinding heats varies. Using these nanoparticles as... For example, according to the Boltzmann distribution principle, Ions in In crystals, due to having Leapfrog channel, Ions undergo electronic transitions under the thermal excitation of grinding, releasing red light. The emission wavelength is concentrated at 612nm, and the intensity of the red light signal increases with increasing temperature.

[0122] In this embodiment, the light signal emitted by the wafer thinning equipment during the wafer grinding process can be collected by the collector and further converted into an electrical signal. For example, if the collector is a photoelectric sensor, the photoelectric sensor can convert the collected light signal into a voltage signal, and then the light intensity value can be obtained by the light intensity detection sensor by identifying the voltage value.

[0123] It should be noted that the signal converted by the collector is not limited to voltage signals, but can also be other forms of intensity-identifiable signals. This application does not impose specific limitations on this. Any electrical or digital signal form that can effectively characterize the intensity of the optical signal and can be identified and processed by subsequent control circuits falls within the protection scope of this application. This includes, but is not limited to, current signals, frequency signals, pulse width modulation (PWM) signals, or digital signals quantized by an analog-to-digital converter (ADC). The choice of signal form can be flexibly determined based on factors such as the circuit design of the specific system, anti-interference requirements, and signal transmission distance. This application does not impose any restrictions on the specific electrical signal representation form of the optical intensity value.

[0124] Understandably, in order to improve the compactness and reliability of the system, the optical signal can also be converted into a voltage signal by the photoelectric converter built into the controller, or the optical signal can be converted into other forms of intensity-identifiable signals by other types of converters built into the controller.

[0125] Furthermore, the controller can also incorporate other types of dedicated signal converters. For example, it can incorporate a voltage-to-frequency converter (VFC) to convert the voltage signal after photoelectric conversion into a square wave signal whose frequency is proportional to the light intensity; or it can incorporate a high-speed ADC to directly quantize the analog light intensity signal into digital code. These converted, other forms of intensity-identifiable signals (such as frequency and digital values) can also be accurately read by the controller's logic units (such as CPU or FPGA) and used for subsequent comparison and judgment logic.

[0126] In one embodiment, for each wafer ground by a grinding wheel, the optical signal output by the collector can be acquired in real time. The collector can acquire the optical signal at a preset sampling frequency and output it. For example, the collector can sample one data point every 0.145ms, corresponding to a sampling frequency of 6.9kHz.

[0127] In one embodiment, to avoid misjudgment due to signal fluctuations, the average of the light intensity values ​​determined a specified number of times can be obtained, and the average of the light intensity values ​​can be used as the output light intensity value. For example, the average of five consecutive determined light intensity values ​​can be calculated as the output light intensity value.

[0128] This embodiment uses a moving average method to process light intensity values, which can effectively suppress noise interference, avoid misjudgments caused by signal fluctuations, and effectively improve the accuracy of light intensity value determination.

[0129] S62. Determine the baseline drift and peak attenuation based on the light intensity value.

[0130] The embodiments of this application can determine the changes in luminescence characteristics based on the changes in light intensity values. The changes in luminescence characteristics can be reflected by the baseline drift and peak attenuation. The changes in luminescence characteristics can reflect the changes in the state of the grinding wheel abrasive. The grinding wheel life can be evaluated based on the changes in the state of the grinding wheel abrasive. Therefore, the embodiments of this application can determine the baseline drift and peak attenuation in real time based on the light intensity values, thereby knowing the state of the grinding wheel in real time.

[0131] In one embodiment, the method for determining baseline drift based on light intensity values ​​includes:

[0132] The current light intensity baseline is determined based on the light intensity value; the baseline drift is determined based on the comparison between the current light intensity baseline and the reference light intensity baseline.

[0133] Based on the definition of the current light intensity baseline, the average light intensity value during the stable grinding phase of the current wafer grinding process can be used as the determined current light intensity baseline. The current light intensity baseline is essentially the average light intensity value during the stable grinding phase of the current wafer grinding process. During the grinding process, the grinding wheel enters the stable grinding phase immediately after each feed. The average of multiple light intensity values ​​monitored during all stable grinding phases is used as the current light intensity baseline. (Refer to...) Figure 5 The reference light intensity baseline is the average light intensity value of the grinding wheel during the stable grinding stage, which is pre-calibrated. Therefore, for a given grinding wheel, its reference light intensity baseline is a fixed value, such as... Figure 5 In this context, Ibase0 refers to multiple line segments parallel to the time axis within the solid line representing the light intensity variation. The current light intensity baseline is the average of multiple light intensity values ​​monitored during the stable grinding phase of the wafer, and it is also a fixed value. Figure 5 Ibase in t1 and Ibase t2 , respectively, refer to multiple line segments parallel to the time axis in the light intensity change line represented by dashed lines, and multiple line segments parallel to the time axis in the light intensity change line represented by dotted lines.

[0134] The baseline drift can be determined using several methods based on the comparison between the current light intensity baseline and the reference light intensity baseline, including:

[0135] The absolute value of the difference between the current light intensity baseline and the reference light intensity baseline can be used as the baseline drift; or,

[0136] The baseline drift is defined as the percentage of the absolute value of the difference between the current light intensity baseline and the reference light intensity baseline compared to the reference light intensity baseline; or...

[0137] Alternatively, the ratio of the current light intensity baseline to the reference light intensity baseline can be calculated as the baseline drift.

[0138] In this embodiment, the baseline drift reflects the fatigue level of the grinding wheel material. Therefore, the grinding wheel's lifespan can be assessed based on the baseline drift, allowing for adjustments to wafer grinding parameters and early warning of wheel replacement timing, thus ensuring grinding accuracy. Figure 5 It can be seen that the current optical intensity baseline Ibase of the wafer under light wear condition during grinding is... t1 Compared with the reference light intensity baseline Ibase t0 There is already a deviation; under severe wear conditions, i.e., end-of-life conditions, the current optical intensity baseline Ibase for grinding the current wafer has been determined. t2 Compared with the reference light intensity baseline Ibase t2The deviation between the two stages is larger than that in the light wear stage. Therefore, the grinding wheel life condition can be evaluated by the baseline drift. The purpose of evaluating the grinding wheel life condition is to facilitate the adjustment of the grinding parameters of the grinding wheel for grinding wafers under different grinding wheel conditions. This ensures that grinding accuracy can be guaranteed under different grinding wheel wear conditions and avoids affecting the quality of wafer grinding.

[0139] In one embodiment, the peak attenuation amount includes: a peak difference attenuation amount; determining the peak attenuation amount based on the light intensity value includes determining the peak difference attenuation amount based on the light intensity value, specifically including:

[0140] The current peak value is determined based on the difference between the peak light intensity at the moment of wafer feed during grinding and the current light intensity baseline; the peak value attenuation is determined based on the comparison between the current peak value difference and the reference peak value difference.

[0141] Because the contact area between the grinding wheel and the wafer is small at each feed, intense friction occurs between the abrasive grains and the wafer surface under high-speed rotation of the grinding wheel, causing a sudden increase in local grinding heat. Therefore, the light intensity reaches its peak. As the abrasive grains wear down, the cutting force at each feed disperses, thus reducing the efficiency of grinding heat generation and gradually decreasing the peak light intensity. In one embodiment, since the light intensity value can be monitored in real time, the maximum value of the light intensity at each feed can be selected as the peak light intensity for one feed. If there are multiple feeds during the grinding process, the average of the maximum values ​​of the light intensity at multiple feeds can be used as the peak light intensity for the current wafer being ground. The difference between the peak light intensity and the current baseline light intensity is used as the current peak value difference for the current wafer being ground.

[0142] The peak difference attenuation can be determined by any of the following methods based on the comparison between the current peak difference and the baseline peak difference:

[0143] The absolute value of the current peak difference and the baseline peak difference can be used as the peak difference attenuation; or,

[0144] Alternatively, the percentage of the absolute value of the current peak difference to the baseline peak difference to the baseline peak difference can be used as the peak attenuation; or,

[0145] Alternatively, the ratio of the current peak difference to the baseline peak difference can be directly calculated as the peak difference attenuation.

[0146] It is understandable that the calculation method for the current peak difference is the same as that for the reference peak difference. If the reference peak difference is calculated as the percentage of the difference between the pre-calibrated peak light intensity at the moment of grinding wheel feed and the reference light intensity baseline, then the corresponding calculation method for the current peak difference is to use the percentage of the difference between the peak light intensity at the moment of feed and the current light intensity baseline as the current peak difference. In other words, the calculation method for the current peak difference is the same as that for the reference peak difference.

[0147] like Figure 5 As shown in the figure, the difference between the highest point of the light intensity variation line represented by the solid line and the reference light intensity baseline is the reference peak difference D0, corresponding to the red vertical solid line in the figure; the difference between the highest point of the light intensity variation line represented by the dashed line and the corresponding light intensity baseline is the current peak difference D under the light wear condition. t1 This corresponds to the red vertical dashed line in the diagram; the difference between the highest point of the light intensity variation line represented by the dotted line and the corresponding light intensity baseline is the current peak difference D under severe wear conditions. t2 As shown by the red vertical dotted line in the diagram; from D0, D t1 and D t2 The change in length shows that as the wear of the grinding wheel increases, the peak difference in light intensity gradually decreases, indicating that the cutting force of the grinding wheel at the moment of feeding is gradually dispersed and the grinding efficiency is gradually decreasing. Therefore, the decrease in the peak difference in light intensity can reflect the increasing wear of abrasive particles.

[0148] The current peak difference can reflect the cutting efficiency of the abrasive grains in real time. Therefore, the change in the cutting efficiency of the abrasive grains can be reflected by the attenuation of the peak difference, thereby judging the grinding wheel life status. Based on the grinding wheel life status, the wafer grinding parameters can be adjusted, and the timing of grinding wheel replacement can be given in advance to ensure the grinding accuracy of the wafer.

[0149] In one embodiment, the peak attenuation amount includes: a peak delay amount; determining the peak attenuation amount based on the light intensity value includes determining the peak delay amount based on the light intensity value, specifically including:

[0150] The time from the start of feed to the appearance of the current peak light intensity of the wafer during grinding is obtained as the current peak appearance time of the wafer during grinding; the peak delay is determined based on the comparison between the current peak appearance time and the reference peak appearance time.

[0151] As the abrasive grains of the grinding wheel wear down, the cutting force at the moment of feed disperses, the efficiency of grinding heat generation slows down, and the time of peak appearance gradually delays. In one embodiment, since the light intensity value can be monitored in real time, the maximum value of the light intensity value at the moment of feed can be selected as the light intensity peak of one feed, and the time corresponding to the maximum value of the light intensity value can be taken as the current peak appearance time; wherein, if there are multiple feeds in the grinding process of the wafer, the average of the current peak appearance times statistically obtained from multiple feeds can be taken as the current peak appearance time of the current wafer being ground by the grinding wheel.

[0152] The method for determining the peak delay based on the comparison between the current peak occurrence time and the baseline peak occurrence time can be any of the following:

[0153] The absolute value of the difference between the current peak occurrence time and the baseline peak occurrence time can be used as the peak delay; or,

[0154] Alternatively, the ratio of the current peak occurrence time to the baseline peak occurrence time can be directly calculated as the peak delay.

[0155] Reference Figure 5 As shown in the figure, Tp0, Tp1, and Tp2 represent the peak occurrence times of the grinding wheel in the unworn, lightly worn, and end-of-life states, respectively. The figure shows that as the wear of the grinding wheel increases, the peak occurrence time gradually delays. Since the peak delay indicates a decrease in grinding efficiency and an increase in the effective cutting contact area between the abrasive grains and the wafer, the current peak occurrence time reflects the lag in the grinding heat generation rate. Therefore, the grinding wheel's lifespan can be determined based on the peak delay, allowing for adjustments to wafer grinding parameters and early warnings of when to replace the grinding wheel, thus ensuring grinding accuracy.

[0156] S63. Compare the baseline drift and peak attenuation with the corresponding thresholds to determine the grinding wheel life status based on the comparison results.

[0157] In this embodiment, different thresholds can be set for the baseline drift and peak attenuation, respectively. The baseline drift and peak attenuation are compared with their respective thresholds to determine the grinding wheel life state based on the comparison results. For example, the baseline drift is compared with a first drift threshold and a second drift threshold, the peak attenuation is compared with a first attenuation threshold and a second attenuation threshold, and the peak delay is compared with a delay threshold. The grinding wheel life state is determined based on the comparison results.

[0158] Furthermore, the wear state of the grinding wheel can be divided into different wear states based on the number of thresholds. For example, the wear states of the grinding wheel include: "normal state", "light wear state" and "severe wear state".

[0159] In one embodiment, determining the grinding wheel life status based on comparisons of baseline drift and peak attenuation with corresponding thresholds includes:

[0160] In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition.

[0161] In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear.

[0162] In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

[0163] In one embodiment, the first drift threshold can be 0.1Ibase0, the second drift threshold is 0.3Ibase0, the first attenuation threshold is 0.2D0, the second attenuation threshold is 0.5D0, and the delay threshold is 0.5Tp0. Here, Ibase0 represents the reference light intensity baseline, D0 represents the reference peak difference, and Tp0 represents the time of occurrence of the reference peak.

[0164] Understandably, when the calculation methods for baseline drift and peak attenuation differ, the thresholds corresponding to each parameter can be converted accordingly to ensure the same judgment result. For example, when calculating baseline drift, if the absolute value of the difference between the current light intensity baseline and the reference light intensity baseline is used as the baseline drift, the corresponding first drift threshold is 0.1Ibase0. If the percentage of the absolute value of the difference between the current light intensity baseline and the reference light intensity baseline to the reference light intensity baseline is used as the baseline drift, then the corresponding first drift threshold of 0.1Ibase0 can be converted to 10%. If the ratio of the current light intensity baseline to the reference light intensity baseline is used as the baseline drift, then the corresponding first drift threshold of 0.1Ibase0 can be converted to 0.9Ibase0. In this case, the judgment of greater than and less than also needs to be converted accordingly. Although the thresholds corresponding to the different methods are different, the judgment result remains the same. Based on the same principle, other thresholds can also be converted in the same way.

[0165] This embodiment simultaneously monitors baseline drift and peak attenuation, and compares them with corresponding thresholds. Compared to a single parameter judgment method, it can more comprehensively capture the changing patterns of optical signal characteristics during the grinding wheel wear process, reduce misjudgments caused by fluctuations of a single parameter, and significantly improve the accuracy of judging the grinding wheel life status, thereby ensuring the precision of wafer grinding.

[0166] Furthermore, this embodiment compares the baseline drift and peak attenuation with corresponding thresholds, and classifies the state of the grinding wheel into different wear states based on the comparison results. Compared with the conventional simple judgment method based on grinding time or the number of wafers processed, its real-time judgment and accuracy are guaranteed. Thus, the grinding parameters can be adjusted according to the real-time evaluation of the grinding wheel's life state to maintain stable grinding efficiency and grinding accuracy, and the wafer grinding quality will not be affected by severe grinding wheel wear.

[0167] In one embodiment, the thinning method further includes:

[0168] Adjusting wafer grinding parameters based on the grinding wheel's lifespan: For example, if the grinding wheel's condition is divided into three states: normal, slightly worn, and severely worn, then in the normal state, the grinding efficiency and stability are both good, and the default initial feed rate can be used. In the slightly worn state, the cutting force of the abrasive grains decreases, and the cutting efficiency also decreases. A preset feed rate can be increased based on the feed rate corresponding to the default grinding parameters to ensure grinding efficiency and accuracy, thus guaranteeing wafer grinding quality. In the severely worn state, the grinding wheel is unsuitable for grinding operations. Therefore, even if the grinding parameters are adjusted, it is impossible to prevent abrasive grains from falling off and damaging the wafer surface. In this case, a new grinding wheel is generally required.

[0169] Understandably, to more precisely control the relationship between grinding parameters and grinding wheel life, the grinding wheel's state can be divided into more states, with different grinding parameters corresponding to different states, thereby ensuring grinding quality and accuracy in each state. And / or

[0170] The system issues corresponding prompts based on the grinding wheel's lifespan. These include: indicating the remaining number of grindable wafers when the grinding wheel is severely worn, allowing for accurate prediction of wheel replacement timing, reducing unexpected downtime, and lowering the defect rate; and issuing a slight wear prompt when the wheel is slightly worn, enabling timely adjustment of grinding parameters to avoid affecting grinding quality. The remaining number of grindable wafers can be determined based on the historical grinding quantity and parameters of the same model of grinding wheel. These prompts help operators promptly identify the grinding wheel's condition, enabling timely responses and preventing a decline in wafer grinding quality and precision due to grinding wheel wear.

[0171] The determination of grinding wheel life status and the corresponding wafer grinding strategy according to one embodiment of this application are shown in Table 2 below.

[0172] Table 2 Grinding Wheel Life Status Judgment and Grinding Strategy

[0173]

[0174] In Table 2 above, ΔI represents the absolute value of the difference between the current light intensity baseline and the reference light intensity baseline;

[0175] ΔD represents the absolute value of the difference between the current peak value and the benchmark peak value;

[0176] ΔTp represents the absolute value of the difference between the time when the baseline peak occurs and the time when the current peak occurs.

[0177] The thinning method of this application acquires the light intensity value corresponding to the optical signal during the wafer grinding process, determines the baseline drift and peak attenuation based on the light intensity value, and determines the grinding wheel life state based on the comparison results of the baseline drift and peak attenuation with corresponding thresholds. This application utilizes the thermoluminescence of nanoparticles in the grinding wheel block to generate light signals of different intensities during wafer grinding caused by different grinding heat. Therefore, the baseline drift and peak attenuation can be determined based on the light intensity value, and the grinding wheel life state can be determined based on the comparison results of the baseline drift and peak attenuation with corresponding thresholds.

[0178] This application embodiment enables the determination of grinding wheel life status based on changes in light intensity characteristics, achieving real-time monitoring of grinding wheel life status. This allows for further adjustment of grinding parameters based on grinding wheel life status, and timely replacement of the grinding wheel in cases of severe wear. This avoids the impact of grinding wheel performance changes on grinding accuracy and damage to the wafer surface caused by severe grinding wheel wear, effectively improving wafer grinding accuracy and efficiency, reducing unexpected downtime, and increasing yield.

[0179] refer to Figure 7 , Figure 7 This is an overall flowchart of a thinning method provided in one embodiment of this application. First, a new grinding wheel is installed, and the wafer thinning equipment is started. Reference calibration includes calibrating: the reference light intensity baseline Ibase0, the reference peak difference D0, and the reference peak occurrence time Tp0. After reference calibration is completed, the grinding operation begins. Optical signals are acquired at a preset sampling frequency, and the corresponding light intensity values ​​are identified. Based on the light intensity values, the real-time parameter Ibase is calculated. t D t ,Tp tThe grinding wheel life status is obtained by comparing each real-time parameter with the corresponding threshold. In this embodiment, when calculating the baseline drift, the ratio of the current light intensity baseline to the reference light intensity baseline is directly calculated, with the first drift threshold being 0.9Ibase0 and the second drift threshold being 0.7Ibase0; when calculating the peak difference attenuation, the ratio of the current peak difference to the reference peak difference is directly calculated, with the first attenuation threshold being 0.8D0 and the second attenuation threshold being 0.5D0; when calculating the peak delay, the ratio of the current peak occurrence time to the reference peak occurrence time is directly calculated, with the corresponding delay threshold being 1.5Tp0; the monitored real-time parameters Ibase0 are compared with the reference peak occurrence time. t D t ,Tp t The results are compared with the above thresholds, and different life states of the grinding wheel are determined based on the comparison results. Specifically, these include:

[0180] If Ibase t ≥0.9Ibase0, and D t If the baseline drift is ≥0.8D0, it means that the baseline drift is within the normal range and the peak difference attenuation is also within the normal range. Therefore, the grinding wheel is judged to be in a normal state, that is, the grinding wheel is not worn. The corresponding strategy is to maintain the current default grinding parameters and continue to monitor.

[0181] If 0.7Ibase0≤Ibase t <0.9Ibase0, or 0.5D0≤D t <0.8D0, 0.7Ibase0≤Ibase t <0.9Ibase0 indicates that the grinding wheel baseline drift has exceeded the normal range, but has not reached a state of severe wear, so the grinding wheel can be judged to be in a state of slight wear; 0.5D0≤D t A value <0.8D0 indicates that the peak difference attenuation of the grinding wheel has exceeded the normal range, but has not reached a state of severe wear. The attenuation of this peak difference can also indicate that the grinding wheel is in a state of slight wear. In this state, the abrasive grains of the grinding wheel have worn, the grinding pressure distribution is somewhat dispersed, and the grinding efficiency has decreased. If the grinding parameters are maintained at the normal level, it will affect the grinding quality. Therefore, the corresponding strategies in this state include issuing a prompt that "the grinding wheel is in a state of slight wear", adjusting the wafer grinding parameters, such as increasing the grinding parameters by 5% based on the initial feed rate, to compensate for the decrease in grinding efficiency and its impact on grinding quality, and continuing to monitor.

[0182] If Ibase t <0.7Ibase0, and D t <0.5D0 and Tp tIf the Tp0 value is greater than 1.5, and all three conditions are met simultaneously, it indicates that the performance of the grinding wheel has deteriorated to an unusable level, indicating that the grinding wheel is in a severely worn state. Continued use of the grinding wheel will damage the wafer surface. The corresponding strategy is to issue an audible and visual warning to "replace the grinding wheel" and suspend grinding to avoid excessive wear of the abrasive grains leading to wafer damage. The audible and visual warning prompts the operator to replace the grinding wheel in a timely manner; suspending grinding can stop the damage and prevent further damage to the wafer from continued operation. It is understandable that if only one or two of the three conditions are met, it means that although the grinding wheel is severely worn, basic grinding requirements can still be maintained by adjusting the grinding parameters, thus avoiding the increased costs associated with frequent grinding wheel replacements.

[0183] This embodiment first performs a benchmark calibration, providing a basis for subsequent determination of baseline drift and peak attenuation. Based on the real-time acquired optical signal and its corresponding light intensity value, the real-time baseline drift and peak attenuation are determined. Comparing these values ​​with corresponding preset thresholds reveals the wear state of the grinding wheel. This helps technicians monitor the wheel's condition at any time. When the grinding wheel is severely worn, it can be replaced promptly, thereby reducing unexpected equipment downtime, lowering the defect rate, and effectively improving grinding efficiency.

[0184] Reference Figure 8 The diagram shown is a structural block diagram of a thinning device 80 provided in one embodiment of this application, including: an acquisition unit 81, a light intensity change analysis unit 82, and a grinding wheel life state determination unit 83.

[0185] The acquisition unit 81 is used to acquire the light intensity value corresponding to the light signal during the grinding process of the wafer; the light signal is emitted by the thermoluminescent nanoparticles in the grinding block under the thermal excitation of grinding.

[0186] Light intensity change analysis unit 82 is used to determine baseline drift and peak attenuation based on light intensity values;

[0187] The grinding wheel life status determination unit 83 is used to compare the baseline drift and peak attenuation with the corresponding thresholds to determine the grinding wheel life status based on the comparison results.

[0188] The further functions of the thinning device in this embodiment refer to the thinning method in the embodiment of this application, and will not be repeated here.

[0189] See Figure 9 , Figure 9 This is a schematic block diagram of an electronic device provided according to an embodiment of this application. Figure 9The electronic device 600 in this embodiment may include one or more processors 601, one or more input devices 602, one or more output devices 603, and one or more memories 604. The processors 601, input devices 602, output devices 603, and memories 604 communicate with each other via a communication bus 605. The memory 604 stores computer programs, including program instructions. The processor 601 executes the program instructions stored in the memory 604. The processor 601 is configured to invoke the program instructions to perform the functions of the units in the above-described device embodiments, for example... Figure 8 The functions of the acquisition unit 81, the light intensity change analysis unit 82, and the grinding wheel life status determination unit 83 are shown.

[0190] It should be understood that, in the embodiments of this application, the processor 601 may be a central processing unit, and the processor may also be other general-purpose processors, digital signal processors, application-specific integrated circuits, etc.

[0191] Input device 602 may include a touchpad, etc., and output device 603 may include a display, speaker, etc.

[0192] The memory 604 may include read-only memory and random access memory, and provides instructions and data to the processor 601. A portion of the memory 604 may also include non-volatile random access memory.

[0193] In specific implementations, the processor 601, input device 602, and output device 603 described in the embodiments of this application can execute the implementation methods described in the thinning method provided in the embodiments of this application. They can also execute the implementation methods of the electronic devices described in the embodiments of this application, which will not be elaborated further here.

[0194] In another embodiment of this application, a computer-readable storage medium is provided. This computer-readable storage medium stores a computer program, which includes program instructions. When executed by a processor, the program instructions implement all or part of the processes in the methods described above. Alternatively, the computer program can instruct related hardware to perform these processes. The computer-readable medium may include any entity or device capable of carrying computer program code, such as a USB flash drive, a portable hard drive, a computer memory, or a read-only memory.

[0195] The computer-readable storage medium can be an internal storage unit of the electronic device in any of the foregoing embodiments, such as a hard disk or memory of the electronic device. The computer-readable storage medium can also be an external storage device of the electronic device, such as a plug-in hard disk, smart memory card, etc., provided on the electronic device.

[0196] This application provides a computer program product, which includes computer-executable instructions or a computer program. The computer-executable instructions or computer program are stored in a computer-readable storage medium. The processor of an electronic device reads the computer-executable instructions from the computer-readable storage medium and executes the computer-executable instructions, causing the electronic device to perform the implementation described in the thinning method provided in this application.

[0197] It should be noted that, depending on the implementation needs, the various components / steps described in the embodiments of this application can be broken down into more components / steps, or two or more components / steps or parts of the operation of components / steps can be combined into new components / steps to achieve the purpose of the embodiments of this application.

[0198] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A wafer thinning equipment, characterized in that, include: An adsorption platform is used to support the wafer and drive its rotation. The grinding device is raised and lowered above the adsorption platform, and has a grinding wheel for grinding wafers at its lower part; the grinding wheel includes a grinding block, which contains thermoluminescent nanoparticles that emit light signals of different intensities under different grinding thermal excitations; A collector is used to collect the optical signal; A controller, electrically connected to the collector, is used to determine baseline drift, peak difference attenuation, and peak delay based on the optical signal; the controller includes: A comparator, electrically connected to the data acquisition unit, is used to compare the baseline drift, peak difference attenuation, and peak delay with corresponding thresholds to determine the grinding wheel life state based on the comparison results, including: In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition. In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear. In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

2. The device according to claim 1, characterized in that, The grinding block comprises diamond abrasive grains with nanoparticles loaded on its surface.

3. The device according to claim 1, characterized in that, The nanoparticles are composed of lanthanide metal oxides.

4. The device according to claim 3, characterized in that, The nanoparticles include one or more of europium oxide, cerium oxide, gadolinium oxide, and samarium oxide.

5. The device according to claim 1, characterized in that, The grinding apparatus includes: A feed assembly is disposed above the adsorption platform and moves up and down relative to it. The feed assembly is electrically connected to the controller, which is configured to control the feed speed of the feed assembly according to the grinding wheel life state. A rotating shaft is connected to and driven by the feed assembly to move up and down, and the grinding wheel is connected to the lower end of the rotating shaft.

6. The device according to claim 1, characterized in that, The controller also includes: A first actuator, electrically connected to the comparator and the feed assembly, is used to adjust the feed rate of the feed assembly based on the grinding wheel life state; and / or The second actuator, electrically connected to the comparator and the indicator, is used to issue corresponding prompts based on the grinding wheel's lifespan status.

7. A thinning method, characterized in that, Includes the following steps: The light intensity value corresponding to the light signal during the grinding process of a wafer is obtained; the light signal is emitted by thermoluminescent nanoparticles in the grinding wheel under the thermal excitation of grinding. The baseline drift, peak difference attenuation, and peak delay are determined based on the light intensity value. The baseline drift, peak difference attenuation, and peak delay are compared with corresponding thresholds to determine the grinding wheel life status based on the comparison results; including: In response to the baseline drift being less than or equal to the first drift threshold and the peak difference attenuation being less than or equal to the first attenuation threshold, the grinding wheel is determined to be in normal condition. In response to the baseline drift being greater than a first drift threshold and less than or equal to a second drift threshold, or the peak difference attenuation being greater than a first attenuation threshold and less than or equal to a second attenuation threshold, the grinding wheel is determined to be in a state of slight wear. In response to the baseline drift being greater than the second drift threshold, the peak difference attenuation being greater than the second attenuation threshold, and the peak delay being greater than the delay threshold, the grinding wheel is determined to be in a severely worn state.

8. The method according to claim 7, characterized in that, Determining the baseline drift based on the light intensity value includes: Determine the current light intensity baseline based on the light intensity value; The baseline drift is determined based on the comparison between the current light intensity baseline and the reference light intensity baseline.

9. The method according to claim 8, characterized in that, Determining the peak difference attenuation based on the light intensity value includes: The current peak value difference is determined based on the difference between the peak light intensity at the moment of wafer feed during grinding and the current light intensity baseline. The peak difference attenuation is determined based on the comparison between the current peak difference and the reference peak difference.

10. The method according to claim 9, characterized in that, Determining the peak delay based on the light intensity value includes: The time elapsed since the start of feed when the peak light intensity of the current wafer appears during grinding is obtained, and this time is taken as the current peak light intensity occurrence time of the current wafer during grinding. The peak delay is determined based on the comparison between the current peak occurrence time and the reference peak occurrence time.

11. The method according to claim 7, characterized in that, The method further includes: Adjust wafer grinding parameters based on grinding wheel life status; and / or The system will issue corresponding prompts based on the grinding wheel's lifespan.

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